Smoke detectors typically have one or more power sources. For example, a smoke detector has a hardwire power source such as mains electricity which supplies AC voltage to the smoke detector. Additionally, the smoke detector has a battery power source. The smoke detector normally operates via the hardwire power source so long as the AC voltage is sufficient to operate the smoke detector. However, if the AC voltage drops below a certain voltage (e.g., due to a brownout or power outage), then the smoke detector operates using the battery power source. In another example, the smoke detector operates exclusively via the battery power source when no hardwire power source is connected to the smoke detector.
In either case, the smoke detector monitors a power level of the battery. When the power level of the battery falls to a level where the battery is not able to operate the smoke detector or reliably operate the smoke detector, the smoke detector outputs an audible sound such as a chirp. The chirp indicates that the battery in the smoke detector needs replacing. This way, with proper servicing, the smoke detector always remains functional.
The drawings are for purpose of illustrating example embodiments, but it is understood that the inventions are not limited to the arrangements and instrumentality shown in the drawings.